The present invention relates to a feed mechanism for moving a signal recording and reproducing head in various disk drive units.
The heads for recording and reproducing signals on and from magnetic disks, optical disks, or other information storage disks in various disk drive units are generally coupled to racks held in mesh with pinions on the output shafts of access motors comprising stepping motors, for example. The rack serves to convert the rotary motion of the pinion to linear motion to drive the signal recording and reproducing head in the radial direction of the disk.
In the disk drive units of the aforesaid design, the position of the head on the disk is dependent on the position where the rack and the pinion mesh with each other, and the head is required to access and trace highly narrow recording tracks on the disk. If, therefore, the meshing engagement between the rack and the pinion is rendered unstable, or if there is a substantial amount of backlash or play between the rack and the pinion, then the head fails to follow the desired recording track accurately, resulting in the degradation of reproduced signals.
Another problem with the conventional disk drive units is that the rack may not remain in proper mesh with the pinion due primarily to a small shock externally imposed on the disk drive unit or abrupt start of rotation of the pinion. Should this happen, the movement of the head is subject to an error, or the rack is liable to be thrown out of mesh with the pinion.